Field of the Invention
The present disclosure relates to the technical field of dual energy CT detection, in particular, relates to a detector device for a dual energy CT system, a dual energy CT system including the detector device and a detection method using the dual energy CT system.
Description of the Related Art
At present, a computer tomography technology (hereinafter referred to as CT technology) based on X-ray radiation imaging is widely used for security inspection, in particular, for inspecting suspicious articles in baggage. In the CT scanning technology based on X-ray radiation imaging, data for characteristic distribution of an object to be scanned in the tomography imaging is obtained by CT data reconstruction. Analysis of such characteristic data contributes to identification of common suspect substance in the baggage. A conventional CT apparatus includes an X-ray source, a collimating device, a rotatable slip-ring, detection units, a dedicated computer system for data calculation, power and control subsystems, etc.
In a conventional dual energy CT structure, the detection unit usually comprises detection crystal units having different energy responses, that is, detection crystal units having a first energy response (e.g., low energy detection crystal units) and detection crystal units having a second energy response (e.g., high energy detection crystal units). Usually, the number of the detection crystal units having a first energy response is equal to that of the detection crystal units having a second energy response. The two types of detection crystal units are provided on two sides of a printed circuit board, respectively. When viewed from incidence direction of the ray, the two types of detection crystal units are aligned with each other (i.e., overlapped) with the printed circuit board being sandwiched therebetween, and the respective detection crystal units having a first energy response corresponds to the respective detection crystal units having a second energy response. During detection, an acquisition module is used to acquire data signals from the detection units, and the acquired data signals are decomposed into data from the detection crystal units having a first energy response and data from the detection crystal units having a second energy response by a dual energy decomposition technology, so as to reconstruct attenuation coefficient images, electron density images and atomic number images of the object in X-ray scanning with different energies. In this way, substance components can be identified and prohibited substance, such as drugs, explosives or the like, can be detected.
For dual energy CT security inspection, sharpness of three-dimension images and identification accuracy of substance are key factors for imaging. However, these two factors require the detector units in different ways. In order to improve sharpness of three-dimension images, it is necessary to increase the number of the detection crystal units having a first energy response or the detection crystal units having a second energy response. However, in order to improve identification accuracy of substance, it is necessary to increase the numbers of the detection crystal units having a first energy response and of the detection crystal units having a second energy response. Furthermore, the number of crystals required for improving sharpness of three-dimension images is much greater than the number of crystal required for improving identification accuracy of substance.
Therefore, in respect that detector crystals are expensive, it is desired to optimize an overall cost of a detector and to ensure a high spatial resolution for CT image reconstruction while meeting requirements for identification accuracy of substance.